Capacitors, which perform many electronic functions, are manufactured using various materials, methods and designs. One of the more common types of capacitors made is the wound capacitor which can be either of the electrolytic or non-electrolytic type.
Wound capacitors generally contain at least two layers of a conductive material, such as a metal foil, with at least one non-conducting spacer layer disposed between adjacent layers of conductive material all wound into a roll and generally protectively packaged. Attached to each conductive layer is means for conducting electricity. Such means generally include at least one metallic lead or tab.
Wound electrolytic capacitors, in addition, contain a quantity of an electrolyte between the conductive layers with the various electrolytes used being well known in the art. Each conductive layer generally comprises a metal foil with an oxide layer formed on some or all of the surfaces of the metal foil.
Wound capacitor rolls and their packaging are usually in a compact cylindrical shape. In most electrical device applications, however, there is sufficient space within the electrical device for all components thereof, including capacitors, thus making the shape of the capacitor relatively unimportant. In some situations, capacitors of other shapes such as oval or flat have been used in order to more efficiently utilize volume within an electrical device when such volume is of an irregular shape and space is at a premium.
Though various capacitor shapes have been utilized, the construction of hollow cored capacitors for use within definite space restrictions entails various problems and difficulties. Known capacitor construction techniques do not produce a satisfactory hollow cored capacitor. Thus, for example, the use of an extra large mandrel during winding produces a hollow cored capacitor roll, but with the roll being too easily deformed during handling. Such capacitor rolls, which are easily distorted may be subject to detrimental variations in capacity and other performance characteristics as a result of such distortions. Further, it is difficult to properly package hollow cored capacitor rolls since generally known packaging techniques encapsulate the entire capacitor rolls and they do not produce a finished capacitor with a hollow core. Known packaging techniques for electrolytic capacitors generally entail such complete encapsulation of the capacitor roll in order to provide reliable seals which prevent electrolyte loss since prevention of electrolyte loss is essential in order to prevent premature capacitor failure.